WASHINGTON — The proportion of Americans who lack health insurance took a big dip last year, with nearly 9 million people gaining coverage since 2013, according to federal figures announced Wednesday morning.

The new figures, from the large annual Census survey that measures Americans’ well-being in several ways, found that the share of people across the country who were uninsured fell from 13.1 percent in 2013 to 10.4 percent last year.

The share of uninsured people in Maine dropped an estimated 1 percentage point, from 147,000 to 134,000. The 13,000 drop comes with a margin of error of 11,000.

At the same time, the nation’s official poverty rate stayed level at 14.8 percent, equivalent to 46.7 million people in poverty. This marks the third consecutive year in which median incomes for Americans remained constant.

Meanwhile, wages continued a long stagnation, with the median household income remaining at $53,657, effectively the same, after being adjusted for inflation, as the year before, showing why so many Americans feel they have not experienced a major improvement in their economic prospects. Income remains 6.5 percent lower than in 2007.

Spreading health insurance to more Americans was a main purpose of the 2010 Affordable Care Act. But from the outset, it was clear it would take years for firm evidence to materialize of whether the law was succeeding at that goal.

The two big strategies built into the law to widen access to health coverage — insurance exchanges selling private health plans to people who cannot get insurance through a job and an expansion of Medicaid for people with lower incomes — took effect at the start of 2014. The new Census report, based on 2014 data, is the first that compares the insurance landscape immediately before those changes began and afterward.

Other surveys lately have indicated that more Americans have been gaining insurance. But another looming question the new report helps answer is how much of this expanded coverage flows from the law and how much is because the nation has been recovering from the Great Recession, so that more people are being hired into jobs that come with health benefits.

Meanwhile, nearly six years since the official end of the recession, the economy was still tough on middle- and low-income families, who have seen only slight improvements to their earnings. In 2013, the poverty rate fell for the first time since 2006, while inequality hovered at the highest it has been since at least the ’90s.

The Census Bureau’s definition of poverty is a rule of thumb developed in the 1960s that is based on triple the minimum amount of money that a household might need to buy food.